A Worldwide Emergency: Arsenic Risk in Water. Case Study of an Abandoned Mine in Italy

Water is an essential resource for the development of human societies. Inadequate availability of good quality water especially in the future will probably cause transboundary and social conflicts. Presently, As contamination in water represents the most relevant risk for many populations in the world, because the diffusion of the contaminant has been facilitated by inappropriate water management, and the effects on the health are serious, though delayed in time. Risk mitigation is expensive and sometimes not completely successful. The case study concerns a small hilly area around an abandoned mine in Sardinia (Italy), and the downstream coastal plain where a subsistence agriculture is developed. Uncontrolled dispersion of wastes from the exploited area and the processing plant, transported downstream, is still affecting (after 40–50 years) the quality of the water in the catchment with concentration of As up to 0.9 mg/l. A study of the As dissolved content in the excavated wells of the plain reveals an irregular spatial distribution with higher values (up to 1 mg/l) in low-lying zones covered by contaminated sediments overflooded from the nearby river. The remediation plan, limited to the hilly area, intends to reduce the supply of contaminant downstream and includes the building of a save dump, where most of the waste-rocks and tailings will be collected, treating the acid waters from the adits on-site, and reclamating in situ small old dumps in the lower part of the catchment